Question

Помогите, пожалуйста!!!

Answer 1

$\frac{2}{\sqrt{3}}(Sin^{4}15^{o}-Cos^{4}15^{o})=\frac{2}{\sqrt{3}}(Sin^{2}15^{o}+Cos^{2}15^{o})(Sin^{2}15^{o}-Cos^{2}15^{o})=\frac{2}{\sqrt{3}}*1*(-Cos30^{o})=-\frac{2}{\sqrt{3}}*\frac{\sqrt{3}}{2}=-1\\\\Otvet:\boxed{-1}$